A base station in a WLAN (wireless local area network) is also referred to as an AP (access point). Currently, in a WLAN system, an OFDM (orthogonal frequency division multiplexing) technology is generally used for transmission. However, to improve system efficiency, introduction of an uplink multi-users technology, such as an uplink OFDMA (orthogonal frequency division multiple access) technology and uplink multi-user MIMO (Multiple-Input Multiple-Output) technology, is under consideration into a standard. In the uplink multi-user technology, a problem that needs to be resolved is how the AP obtains an uplink data request of a STA (station).
Currently, there are multiple technologies for obtaining the uplink data request of the STA.
In a first technology, the uplink data request is obtained by means of random competition. Because random competition does not need a central station to control a network, random competition has a simple structure and flexible networking and is widely applied to a distributed network. However, when system load is very large and competition increases, conflict avoidance is relatively difficult, and an access requirement of a specific service cannot be met.
In a second technology, the uplink data request is obtained by means of polling. That is, the AP specifies multiple STAs to send uplink data requests on specified sub-channels by means of OFDMA. Because it is unknown which STAs have cached data, polling is blindly performed. As a result, system efficiency is reduced because the AP polls a large quantity of STAs that have no uplink data.